The Effect of an In-shoe Orthotic Heel Lift on Loading of the Achilles Tendon During Shod Walking

Controlled laboratory study. Orthotic heel lifts are thought to lower tension in the Achilles tendon, but evidence for this effect is equivocal. To investigate the effect of a 12-mm, in-shoe orthotic heel lift on Achilles tendon loading during shod walking using transmission-mode ultrasonography. The propagation speed of ultrasound, which is governed by the elastic modulus and density of tendon and proportional to the tensile load to which it is exposed, was measured in the right Achilles tendon of 12 recreationally active men during shod treadmill walking at matched speeds (3.4 ± 0.7 km/h), with and without addition of a heel lift. Vertical ground reaction force and spatiotemporal gait parameters were simultaneously recorded. Data were acquired at 100 Hz during 10 seconds of steady-state walking. Statistical comparisons were made using paired t tests (α = .05). Ultrasound transmission speed in the Achilles tendon was characterized by 2 maxima (P1, P2) and minima (M1, M2) during walking. Addition of a heel lift to footwear resulted in a 2% increase and 2% decrease in the first vertical ground reaction force peak and the local minimum, respectively (P